EDIT: Just saw your post above, but I'm wondering strictly from a street comfort point of view...

I don't know. That's a good question if you were to compare a Monotube vs Twin-Tube manufactured at the same cost and sold for the same price for a street coil over, let's say $1500. Which would be more comfortable?

Cool, I'll take a look at that. Maybe it's different with the lower end AST 4100s...

I know that Charles initially bought a set of AST 4200's and was faced with a few major problems. I also know that the Bimmerworks race team has a set of AST 4x00's and is also unsatisfied. I don't know the specifics why, but I haven't really heard great things about the AST 4xxx series.

So far my 5200's have held up phenomenally. I've got approximately 5 hours of track time on them and about 15k street miles.

How are these Nitrons? VAC recommended them to me. It does come with camber plates, so that's a plus. But I see two issues here: M3 fitment (need M3 rear camber arms); the picture does not show the rear springs and dampers separately. I've read some scary things about converting to "true" coilovers in the rear for our cars.

On a serious note, HPA has the 5200's for ~$1.5k more than TCK DAs. I have no doubt that they are better.

I'm still convinced that TCK offers the best bang for the buck.

OP: Hit up Harold@HPA. He sells all of the products mentioned in this thread and will have the best advice on these forums. It's up to you to determine where the price gets a little steep. For me, when I start looking at 50% $$ of a Spec e30 in just suspension for my DD, I draw the line, lol.

Both TCK DA's and AST 5200's are great products, but TCK DA's are better compared to the AST 4200(no external canisters).

We competed in Redline Time Attack for 2 years with reworked(re-valved for much higher rate springs) TCK DA's and had great results. We were the only Koni equipped competitor in our class, everyone else were on KW's or something else. We also sponsored a stock class driver with TCK DA's on his E92 M3 and he has had a couple podium finishes as well. Our driver who has had plenty of seat time on KW's said the Koni's were much better in damping than KW's.

This debate can go on forever, I recommend buying the best name brand dampers you are afford and you will be happy that you did.

That is a lot of information :-) I am concentrating a focus here on cars that are used for both street and track...The vast majority of people reading this drive their car every day and enjoy the track too!

I will try to give an explanation of most of the above info. that is easily understood...

High presure gas mono-tube dampers do have a difficult time absorbing the initial bump (compression) because of all the pressure. Therefore the dampers transmit all the energy through the chassis. This is why so many BMW owners feel that the ride is harsh with brands that utilize a high pressure gas system. However, on a smooth surface like a racetrack you don't typically experience that issue.

Low pressure gas twin-tube dampers (Many TC Kline are NO pressure) are able to absorb the bump far more efficiently (more comfortably) because there is not huge amounts of initial resistance fighting against the compression force. It is, as stated above, a progressive damper of sort. As for the cavitation issue...Koni uses an extremely high quality oil that does not have cavitation issues. So the initial reasoning for the development of the mono-tube design is simply not an issue with the Koni product line.

So, in a nutshell, the low pressure/no pressure gas damper is a better choice for those who are using the vehicle as a dual purpose car. Additionally, the twin tube design has the ability to achieve more stroke (suspension travel) based on the body length of the damper vs. a mono-tube design. Again, for lowered street driven cars is a major bonus!

This is all under the assumption that the damper is equipped with a high quality valving package to give you the precise handling dynamic you are looking for!

I hope this helps explain the differences in an easily understood manor!

I don't know. That's a good question if you were to compare a Monotube vs Twin-Tube manufactured at the same cost and sold for the same price for a street coil over, let's say $1500. Which would be more comfortable?

That's going to take someone with more knowledge than me to answer.

It is not a matter of just getting a suspension that is monotube vs. twin tube. It is more dependant on getting a product that has high quality internals. There are an increasing number of products on the market but unfortunately you cannot see what is on the inside or how the valving package works (not all manufacturers want you to know) But know that Koni products are tried and true and twin-tube design of the koni's have what it takes to absorb the high compression bumps that you experience on the street and the versatility to adjust them to be spectacular on track/autocross!

For instance - just because suspension XYZ has 30 adjustments it doesn't mean that each of the settings makes a difference in the flow of fluid through the valves great enough to warrant the functional range of adjustments.

For instance - just because suspension XYZ has 30 adjustments it doesn't mean that each of the settings makes a difference in the flow of fluid through the valves great enough to warrant the functional range of adjustments.

I was reading that the needle valve adjustments of the cheaper coilovers make very little difference throughout their adjustment range. Ala 1/30 feels pretty much the same as 10/30 while 30/30 may have a difference with 1/30.

On the other hand, I'm feeling a major difference between every click out of my 1/10 rebound settings on AST's.

I think at the end of the day, the OT is going to have a great opportunity to test a number of these coilovers at the track with a huge number of e90post members going to the same event. He'll probably come back with a verdict then as to the feel of each.

HPA is a preferred dealer for TC Kline products.
The two kits are the same with the exception the HPA offers the Swift springs as well as some other complimenting parts.

Now - ther difference between the single adjustable and thedouble adjustable...

The single adjustable (AKA: True Match) offers a similar valving package to the Koni Sport shocks but with height adjustability and external rebound adjustment. The difference in the valving between the Koni sport and the TC Kline Racing Koni is - the upper end of the rebound damping is firmer than the Koni sport.

The double adjustable (AKA: Smart Design) has a completely different internal valving package. All the internals are motorsports valving where the precision of the movement of fluid is compared to the performance of much more expensive suspensions like Moton and JRZ, etc. The great thing about our suspension is that it can be adjusted to be far better than stock on the street AND it has race winning performance on the track!

I have yet to hear about why M3 control arms are better than non-M.. if anyone has comments on these..

M3 components vs. non-M - most of the differences are that the M3 are aluminum. The M3 are a bit longer so they give you better negative camber settings. And some of the bushings are replaced with monoball bushings vs. rubber!

i love it, use 94% daily driven, 6% track. i did not initially get camber plates, however they are going in next week!

my brief review is the kit it very capable and more then sufficient for daily driving. makes driving to work a blast! i have tracked it once and was shocked how capable it was there too. the car did not get upset at all at thunderbolt and i don't consider my self an advanced driver

a good alignment is important as well. PSS also have helped this kit shine

Regarding comments that monotubes are harsher and everything else said about monotubes ... I'm not going to disagree with those comments or anyone here, and will just state why JRZ is not included in the generalizations. I consider JRZ on a separate playing field entirely. They are a VERY different product. I would go as far to say as they design dampers with a different end goal than most dampers companies and I therefore consider them incomparable with nearly all other dampers (ok, I'll make accommodations for Motons and ludicrously-priced Penskes ...).

Jan Zuijdijk founded JRZ. He invented modern day damping in the 70s. This is his book:http://www.amazon.com/Vehicle-dynami.../dp/1449059163
It's a horrific translation into English but if you can stand it, you'll 'get' it - what a damper is supposed to be, and why the dampers in most cars ... aren't. The book is more of a philosophical take and as a JRZ customer, I can vouch it translates well into the real world.

***Regarding harshness - JRZ dampers are not harsh. I can drive around all day at full stiffness in Philadelphia. There is no difference in harshness between 1/24 click and 24/24 click. Two of the reasons this is possible via JRZ's design:
-a large piston rod
-non-preloaded valves
Most dampers use preloaded discs/shimms which prior to opening, will build up force equal to the preload meaning a harsh initial compression; and those dampers must compensate for that preload via valving compromises which further degrades the damping quality. There is no such thing with JRZ since they are not preloaded and JRZ's piston rod is specially designed to work with non-preloaded discs. The piston rod has primary and secondary deflective disc stacks which vary the damping forces depending on the piston velocity; hence JRZ is able to provide the exact amount of damping force required in any situation, no more, no less.

***Smoothness - this is a determinant of damping quality (quality referring to the ability to effectively control forces) so the internal fluid transfers inside a JRZ damper are as smooth as possible. This includes the internal orifices where fluid passes through but also the damper tube itself; JRZ uses high strength aluminum and the tube is formed by extrusion. That means it is the same diameter inside down to the micron and extremely smooth.

***Unsprung mass support - a damper's purpose is to control the forces between the unspring and sprung mass so logically that means it must control both. Most dampers are designed to control the sprung mass - aka the car body and half the suspension. A damper focusing on that is only doing part of the job and is reactive instead of active.
JRZ of course controls the sprung mass but the difference is that they focus on unsprung mass too - which is more important since it initiates the forces on the sprung mass. Think about it.
JRZ's unsprung mass control is a combination of their method of gas pressure volume selection (which adds lifting force to the entire stroke of the piston rod), the large piston rod itself (which is a multiplier for the lifting force, hence it is as large as possible), and the smoothness of the internal fluid transfers.
*Smaller point about gas pressures - most monotube dampers use it to keep the fluid compressed, which JRZ does as well. The difference is JRZ does not use gas pressure as a crutch to generate forces, especially compression (more like a twin-tube in this regard). That is very unlike a standard monotube damper design philosophy.

I wrote more than I wanted to but it has the intended effect. Most standard damper design papers and write-ups I read missed all the above and I did not understand it either until I had a proper damper installed. All of the above is some of my reasoning for why a JRZ damper is not on the same playing field. There is nil to compare here.

No offense to any vendors, of course. Nor am I advocating everyone buy JRZs, as they are rather steeply priced. I'm sure if I bought TCK S/A I would be a happy customer. And I still got around the track with my stock Bilstein B4s. JRZ is different. Better in my opinion, but that's what I want to stress - different. Different philosophy, different goals, very different result.

Edit: I'll have another writeup about my experiences on the track w/ JRZ; I took the car to Summit Point this past weekend but want to get a few more sessions under my belt before saying anything. As a teaser - the only thing I'm feeling in my car is ... the tire's contact patch. Ya...

Regarding comments that monotubes are harsher and everything else said about monotubes ... I'm not going to disagree with those comments or anyone here, and will just state why JRZ is not included in the generalizations. I consider JRZ on a separate playing field entirely. They are a VERY different product. I would go as far to say as they design dampers with a different end goal than most dampers companies and I therefore consider them incomparable with nearly all other dampers (ok, I'll make accommodations for Motons and ludicrously-priced Penskes ...).

......edited to save room...

I wrote more than I wanted to but it has the intended effect. Most standard damper design papers and write-ups I read missed all the above and I did not understand it either until I had a proper damper installed. All of the above is some of my reasoning for why a JRZ damper is not on the same playing field. There is nil to compare here.

No offense to any vendors, of course. Nor am I advocating everyone buy JRZs, as they are rather steeply priced. I'm sure if I bought TCK S/A I would be a happy customer. And I still got around the track with my stock Bilstein B4s. JRZ is different. Better in my opinion, but that's what I want to stress - different. Different philosophy, different goals, very different result.

Edit: I'll have another writeup about my experiences on the track w/ JRZ; I took the car to Summit Point this past weekend but want to get a few more sessions under my belt before saying anything. As a teaser - the only thing I'm feeling in my car is ... the tire's contact patch. Ya...

@wonho, look what your thread turned into.

Your post and feedback is awesome and there is no doubt that JRZ has done a fantastic job of providing a very high end product!

TC Kline Racing offers an exceptional value for our single and double adjustable suspensions for the price. The fact that our double adjustable racing suspension gives equal performance for a fraction of the cost of the more expensive options is what we try to promote and they come with a lifetime warranty

The kit that includes M3 rear camber arms are about 250 more. What would be the benefit of this conversion btw, other than more availability of "proper" race coilovers?

I def agree best value either way. I just hope their kit's Eibach springs are somewhat comparable to the TCKR or Swift springs.

M3 camber arms are aluminum instead of stamped steel. The lower shock mounts eliminate the rubber saddle of the oe arms, and I believe the bushings that mount to the subframe are firmer than oe. You can't get a set of M3 camber arms for $250 anywhere else.
Springs are springs. I'm sure GC has Eibachs in any spring rate you want.
btw, if you're increasing spring rate, you should budget for M3 or firmer subframe bushings.